Reprinted from the New York Medical Journal 
for May If 1895. 
THE DIAGNOSIS OF 
LESIONS OF THE LUMBAR CORD, 
CAUDA EQUINA, AND CONUS MEDULLARIS* 
By FREDERICK PETERSON, M. D., 
CHIEF OF CLINIC, NERVOUS DEPARTMENT, VANDERBILT CLINIC, 
COLLEGE OF PHYSICIANS AND SURGEONS, NEW YORK. 
As an evidence of the progress of neurological science 
of late years, there is perhaps nothing more interesting 
than the unraveling of the mysteries of the tracts and cen- 
ters and nerve trunks of the lower part of the spinal cord. 
We are now in a position to make very accurate diagnoses 
of the nature and position of lesions in the lower part of 
the spinal canal from a study of the peculiar distribution 
of anaesthesias, the extent and character of paralyses, and 
the disturbances of various reflexes. Then, too, lesions in 
this part of the organism, such as caries, spinal injuries, 
haemorrhages, and neoplasms, are not so rare but that a 
brief exposition of the points of differential diagnosis 
should be of service to every physician. 
The lumbar enlargement of the cord lies in the spinal 
* Read before the Hospital Graduates' Club, February 28, 1895. 
Copyright, 1895, by D. Appleton and Company. 200 
THE DIAGNOSIS OF 
canal opposite to the space between the lower portions of 
the tips of the tenth dorsal and first lumbar spines. Thus 
the spinal canal is twenty six 
to twenty-eight inches long, 
and the spinal cord is only 
seventeen or eighteen inches 
long. The remaining space 
of nine or ten inches of the 
canal is occupied by the cauda 
equina, composed of the lum- 
bo-sacral nerve trunks coming 
off from the lumbar enlarge- 
ment of the cord. The termi- 
nation of the cord at the lower 
border of the 
first lumbar ver- 
tebra is not al- 
ways kept suf- 
ficiently distinct 
in the mind of 
the student or physician. I 
have seen, for instance, a 
physician seeking for cord 
symptoms in a fracture of one 
of the lower lumbar verte- 
brae. 
The lumbar enlargement of 
the cord has in its anterior 
horns the trophic centers for all of the muscles of the 
lower extremities. Into it pass all the sensory fibers from 
the lower extremities, genitals, rectum, and nates. In it 
are the reflex centers for such important reflexes as the 
knee-jerk, ankle-clonus, cremasteric, plantar, and gluteal 
reflexes. And here, too, are the centers for the sphincters 
Tenth dorsal spine. 
First lumbar spine LESIONS OF THE LUMBAR CORD. 
201 
of the bladder and rectum, and for erection, menstruation, 
and parturition. 
These various organs and functions are represented 
I 
CREMASTERIC 
Abdomen added here. Above this point all anaesthesia in a girdle form about the trunk 
2 
Ilio-psoas 
Sartorius 
In front, all below line of Poupart's ligament. Behind, all beloiv transverse lumbar lines 
Biceps 
Rotators of thighs 
KNEE JERK 
.Back of legs, both back and front of thighs. Anaesthesia over all except funnel- 
shaped area along front of thigh and leg down to foot 
3 
Adductor of thigh 
Tibialis anticus 
Peroneus longus 
G LUT EAL 
4 
Rotators of thighs' 
Flexors of ankles 
Extensors of Toes 
Peronei 
ANKLE 
CLONUS 
Extension farther over, outer sides, both legs to feet 
5 
REF1LEX 
I 
PLANTAR 
Extension of anaesthesia downward 
to popliteal space 
2 
3 
Saddle shaped area 
BLiADDER| 
RECTUM 
Perinceum Scrotum 
posterior surface of 
the penis, rectum, vagina 
4 
5 
Conus 202 
THE DIAGNOSIS OF 
serially in the segments which constitute the lumbar en- 
largement, five lumbar and five sacral segments. The cen- 
ters for the lowest muscles of the lowrer extremities are in 
the lower segments of this enlargement, and the higher the 
situation of the muscles in these extremities the higher the 
representation in the segments. There is also a segmental 
sensory distribution, only the areas of sensibility run 
lengthwise down the extremities, and require special study 
in order to appreciate their relations to the nerve trunks 
and segments of the cord. The diagram submitted will be 
helpful to this end. 
Thus destructive lesion of the fourth and fifth sacral 
segments causes anaesthesia of the perinaeum, posterior sur- 
face of the penis, scrotum, rectum, and vagina. At the third 
sacral segment this area is extended out over the buttocks 
and downward on the backs of the thighs, so that the area 
corresponds to that touched when seated in a saddle. The 
higher the lesion the greater the extent of this anaesthesia. 
The peculiarities of this distribution are noted in the dia- 
gram. The reflexes have their particular segmental centers. 
Thus of the very important ones, the knee-jerk center is in 
the third lumbar segment, the ankle-clonus in the fifth 
lumbar segment, the cremasteric in the three upper lumbar, 
and the bladder and rectum in the lowest point of the cord, 
in the fourth and fifth sacral segments and the conus. By 
some authorities this club-shaped tip of the cord, the 
conus medullaris or conus terminalis, is supposed to be ex- 
clusively the center for the vesical and rectal reflexes, 
though this is not proved. 
We must remember, in this consideration of the seg- 
mental arrangement of the muscles, reflexes, and so on, in the 
lumbar cord, that there are also in the lateral columns fibers 
coming down from the brain which convey motor im- 
pulses from above to the muscles and which also inhibit LESIONS OF THE LUMBAR CORD. 
203 
the reflexes. Thus a lesion in the second lumbar segment 
might exaggerate the knee-jerk and cause ankle clonus, be- 
cause of the inhibitory fibers to these centers being affected. 
On the other hand, a lesion in the third lumbar segment 
may give us the very singular phenomenon of lost knee-jerks 
in conjunction with ankle clonus. 
Now, the cauda equina is composed chiefly of the great 
nerve trunks arising from this lumbar enlargement, one 
pair from each segment, and hence each pair of nerves 
represents the motor, trophic, sensory, and reflex functions 
of the segment from which it springs. Any lesion of them 
must necessarily cause much the same effects as would 
arise from lesions of the segments from which they come. 
Thus lesions affecting the sacral nerve roots produce the 
same anaesthetic areas as do lesions of the sacral part of 
the cord, together with paralysis of the bladder and rectum. 
A lack of symmetry on the two sides in the distribution of 
the paralyses and the anaesthetic areas would be, however, 
presumptive of a cauda rather than a cord lesion. An ex- 
ceedingly slow and irregular development of the symptoms 
would also suggest a cauda lesion. But it is not always 
easy to distinguish cauda from spinal-cord lesions, and the 
fact must be borne in mind that often both the cauda and 
the lower part of the cord are involved together in the 
pathological process. 
It has been demonstrated that pressure on the cauda 
equina affects to a greater degree the nerves in the middle 
of the cauda than those near the surface (Thorburn). The 
lower nerve roots of the cauda are nearer the middle line 
than the nerves which pass out above them; and when 
pressure is brought to bear upon the cauda, the nerves 
which pass out at the lower level are more seriously af- 
fected than those emerging above them. 
]n lesions such as haemorrhage or compression, where im- 204 
THE DIAGNOSIS OF 
provement may take place, the upper roots are apt to show 
signs of a change for the better soonest, and may indeed 
recover completely, while the lower ones remain as before. 
Pressure upon the nerves of the cauda is often suffi- 
cient to produce widespread paralysis when sensation is 
but slightly affected (Starr). This is often of value in a 
differential diagnosis, since lesions of the same magnitude 
in the lumbar enlargement would produce only a moderate 
amount of paralysis, depending upon the segment or seg- 
ments involved. 
In traumatic conditions the external evidence of frac- 
ture below the first lumbar vertebra, affecting the lumbar 
or sacral portions of the spinal column, would be an im- 
portant indication of involvement of the cauda equina. 
Pain and tenderness over the lumbo-sacral regions have 
been noted in some of the cases of lesions of the cauda 
equina, such as neoplasms. The pain is nearly always 
chiefly sacral. 
In cauda lesions the sciatic and pudic and sometimes 
the anterior crural and obturator nerves are particularly 
apt to suffer. Whether the degenerative reaction in the mus- 
cles supplied by the affected nerves will be present depends 
naturally upon the amount of damage done to them, which 
is variable. 
As to the reflexes, the knee-jerks will be absent if the 
nerves to the anterior thigh muscles are affected. In no 
case of purely caudal lesion will they be exaggerated. The 
plantar reflexes are usually absent. The extent of the le- 
sion in the cauda will determine to what degree the sphinc- 
ters are disturbed. Disorder of the mechanism governing 
the sphincters of the bladder and rectum will depend upon 
whether their particular nerves are involved and to what 
degree. Urinary retention with overflow incontinence is 
not very frequent in cauda lesion, and when it does exist LESIONS OF THE LUMBAR CORD. 
205 
may be recovered from as pressure diminishes. The pres- 
ence of complete paralysis of the bladder and rectum is 
rather suggestive of coincident lesion of the lower tip of 
the cord. 
Bedsores, and sometimes perforating ulcers, occur in a 
certain number of cases of cauda lesion. 
In some instances it may be necessary to differentiate 
peripheral nerve lesions, such as multiple neuritis and dis- 
orders of the lumbar and sacral plexuses. Ordinary multiple 
neuritis presents no difficulty, but a bilateral lumbo-sacral 
neuritis may offer obstacles in the way of diagnosis for 
some time until absolutely characteristic symptoms have 
appeared. In other lumbo-sacral plexus lesions a bilateral 
manifestation of symptoms should form a diagnosis of 
cauda disorder, though in some very rare instances the 
cauda lesion may involve but one side and thus give rise to 
confusion. 
Occasionally a lesion of the cauda (tumor) may for a 
time simulate locomotor ataxia by presenting some of the 
symptoms common to both-viz., loss of knee jerks, dis- 
order of the bladder sphincter, sharp pains radiating down 
the legs, and peculiarity of gait. But there will be no 
ataxia, and papillary symptoms will be wanting, while atro- 
phies and anaesthesias are almost certain to develop in the 
course of time and thus demonstrate the presence of a cauda 
lesion. 
The most common of all lesions affecting the cauda is 
fracture and dislocation of the lumbar spine, compressing 
or crushing the nerve roots, or both. Moderate dislocation 
of the vertebra may cause little damage, because of the 
large size of the canal and the small part of it occupied by 
the nerves. The symptoms will vary with the extent and 
degree of the injury. Haemorrhage is another though in- 
frequent lesion of the cauda equina. Much more common 206 
THE diagnosis of lesions of the lumbar cord. 
than this are neoplasms. Among the tumors which have 
been described as developing in this part of the vertebral 
canal and affecting the cauda equina are sarcoma, fibro- 
sarcoma, meningocele in spina bifida, gumma, cavernous 
angeioma, and multiple neuromata. 
The chief characteristics of tumor compression of the 
cauda equina are slow and progressive development of the 
atrophic paralyses, reflex disorders and anaesthesias pecul- 
iar to the region, and intense and increasing sacral pain 
of a radiating character, and sacral tenderness. Sometimes 
retrogression may take place, or the growth be temporarily 
arrested. 
As regards isolated lesions of the conus medullaris, it 
has become current in neurological literature to a certain 
extent that we have from such complete paralysis of the 
bladder and rectum. This would mean that the vesical and 
rectal reflex centers then were situated wholly in the conus. 
But, as far as I can learn from a careful search of the 
literature, this current idea is based upon two cases report- 
ed respectively by Oppenheim and Lochmann. Oppenheim 
{Arch. f. Psych., xx, 1889, p. 298) has a paper Ueber eine 
sich auf den Conus Terminalis des Rilckenmarks beschran- 
kende traumatische Erkrankung; but, on reading his paper 
and the result of the autopsy, 1 find it is not at all a case 
of " traumatic disease limited to the conus terminalis," for 
he describes how the changes become less marked in the 
sacral portion of the cord, and still less so in the lumbar 
portion. Lochmann's case, too, is not wholly satisfactory 
in this respect.